This invention relates to an electric circuit in an instrument for detecting ultra-violet radiation, visible light or infrared radiation, comprising a photo-diode of silicon or germanium, a precision resistor for measuring, via which generated photo-electric current from the photo-diode generates a voltage, and a voltmeter with low leakage current for measuring the voltage generated.
The present invention has as an object to render possible a structural design, which is less expensive, simpler and safer than the ones known and commercially available.
The invention is characterized in that the precision resistor and calibrated voltmeter each are connected in parallel with the photo-diode.